/Engine/Plugins/Online/OnlineFramework/Source/Party/Public/Party/SocialParty.h
void RequestJoinInProgress ( const [UPartyMember](API\Plugins\Party\Party\UPartyMember) & TargetMember, const [FOnRequestJoinInProgressComplete](API\Plugins\Party\Party\USocialParty\FOnRequestJoinInProgressComplete) & CompletionDelegate )